A goal of the third generation partnership project (3GPP) long term evolution (LTE) program is to develop new technology, new architecture and new methods for LTE settings and configurations in order to provide improved spectral efficiency, reduced latency, and better utilization of radio resources for faster user experiences and richer applications and lower cost services. As part of these efforts, the 3GPP has introduced the concept of an in-home evolved Node-B (HeNB) for LTE networks. 3GPP is also considering an in-home Node-B (HNB) for release 8 (R8) wideband code division multiple access (WCDMA).
The HeNB refers to a physical device that may be similar to a wireless local area network (WLAN) access point (AP). The HeNB provides users with access to LTE services over extremely small service areas, such as homes or small offices. The HeNB is intended to connect to the operators' core network by using, for example, the public internet connections available freely today at homes across the country, (e.g., digital subscriber line (DSL)). This can be particularly useful in areas where LTE has not been deployed, and/or in areas where legacy 3GPP radio access technology (RAT) coverage already exists. This may also be useful in areas where LTE coverage may be faint or non-existent due to, for example, the occurrence of radio transmission problems in an underground metro or a shopping mall.
An HeNB closed subscriber group (CSG) cell is a defined area over which radio coverage provided by the HeNB may only be accessed by a group of subscribers authorized to use the services of the cell. The CSG may be a family or anyone in the vicinity of a particular location, (e.g., anyone in a coffee shop), who attempts to access the HeNB CSG cell. An HeNB may typically be used to deploy one or more CSG cells over an area over which LTE coverage is desired. A CSG cell may be deployed by an HeNB for LTE services, or by an HNB for WCDMA or other legacy 3GPP RAT services. The subscriber, whether an individual or an organization, may deploy a CSG cell using an HeNB over an area where such service is desired.
FIG. 1 shows an example of a conventional HeNB deployment in a wireless communication system 100. The wireless communication system 100 includes an LTE macro-cell 105, a 3GPP system cell 110, a higher network node (e.g., gateway) 115 and/or a mobility management entity (MME)/serving general packet radio service (GPRS) support node (SGSN) 120. The higher network node 115 is responsible for coordinating the operation of several HeNBs 125A, 125B and 125C. Alternatively, the MME/SGSN 120 may be responsible for coordinating the operation of several HeNBs 125A, 125B and 125C. The MME is the LTE equivalent of a 3G/2G SGSN. The relationship between the LTE macro-cell 105 and the 3GPP system 110, (e.g., WCDMA/global system for mobile communications (GSM)), is that there may be areas where the coverage of these two technologies overlap. It is similar to simultaneous coverage of GSM and WCDMA technologies. The relationship of the LTE macro-cell 105 and the 3GPP system cell 110 with the higher network node 115 is ambiguous. In all likelihood, the higher network node 115 is likely to be a gateway function which interfaces with the MME/SGSN 120. As a gateway, the role of the higher network node 115 may be to act as a single macro-cell towards the MME/SGSN 120 while supporting several small home cells.
CSG cells may belong to a tracking area (TA) that is different from that of the surrounding macro-cell. Such a TA may be referred to as a CSG TA, as disclosed in copending U.S. patent application Ser. No. 12/044,491 filed on Mar. 7, 2008, which is incorporated by reference as if fully set forth. The surrounding macro-cell is usually relatively large (e.g., covers at least several square blocks), and is deployed by the operator by using an e-Node-B, (i.e., a base station). The HeNB is a miniature base station which is deployed at home, and the cell provided by the HeNB covers only a small area in the home.
A cell broadcast is a large message that a cell sends out on a particular common physical channel, (i.e., the broadcast channel), that can be read by all wireless transmit/receive units (WTRUs) in the cell. The cell broadcast carries information that is necessary for each of the WTRUs to know, such as what cell, network and the like the WTRU is accessing and what features are supported. The CSG cell may indicate in its cell broadcast whether the TA broadcast is a CSG TA, as identified by a special tag or information element (IE) in the cell broadcast, or a regular TA as identified by the absence of any special marker. The WTRU can then check its subscription, either in a memory device, (e.g., a universal subscriber identity module (USIM) residing in a universal integrated circuit card (UICC)), in the WTRU, or its LTE equivalent, (which may be any other application on the UICC), to see if the WTRU has access to this CSG cell.
FIG. 2 shows a conventional wireless communication system in which CSG identification using a unique TA for each CSG cell is implemented, whereby each CSG identifier (ID), (e.g., 1500, 1501, 1502, 1503), is the same as the CSG TA of the CSG cell. However, this poses a problem because assigning a unique tracking area code (TAC) to each CSG cell may not be feasible as then there would be a very large number of TAs and a corresponding requirement of a large number of unique TACs. Alternatively, if several CSG cells are assigned to a single TA, access control may be problematic as WTRUs can access each CSG cell that is assigned to a particular TA instead of just their own.
Another issue that needs to be addressed is determining how WTRUs should be added or removed from the list of WTRUs that are allowed to access the CSG cell. Yet another issue that needs to be addressed is determining whether a CSG cell can accept traffic from a limited set of users, for instance, the close family, or can a CSG cell accept traffic from a pedestrian user passing on the street.